The present invention relates to a blood perfusion system used during surgery such as cardiovascular surgery wherein air emboli present in the perfusion circuit is efficiently removed by an air removal device before returning the embolus-free blood back to circulation in the patient.
During cardiac bypass surgery, the heart is stopped in order to allow repair of defects, such as the replacement of defective heart valves, or the placement of bypass grafts. The patient's blood is redirected through an extracorporeal perfusion circuit typically including various items such as a venous cannula, PVC tubing, a reservoir, a pump, an oxygenator, an arterial filter, and an arterial cannula. During extraction of blood from the patient and/or at various stages of flow within the perfusion circuit, air emboli may form within the circulating blood. If these emboli are not removed from the circulating blood and are instead introduced back to the patient's bloodstream, there may be serious complications.
Air or other gaseous emboli can be removed (i.e., filtered) from blood that is flowing in a perfusion circuit by passing it through an air removal system. A screen or mesh filter can be employed for this purpose. Other examples of air removal devices that can be used include those shown in co-pending U.S. application Ser. No. 11/118,726, filed Apr. 29, 2005, entitled “Air Removal Device with Float Valve for Blood Perfusion System”, co-pending U.S. application Ser. No. 11/136,047, filed May 24, 2005, entitled “Vortex-Flow Air Removal in a Blood Perfusion System”, co-pending U.S. application Ser. No. 11/245,751, filed Oct. 7, 2005, entitled “Float-Driven Lever Arm for Blood Perfusion Air Removal Device”, and co-pending U.S. application Ser. No. 11/245,752, filed Oct. 7, 2005, entitled “Blood Perfusion Air Removal Device with Arcuate Manifold”, all of which are incorporated herein by reference in their entirety.
Some currently available perfusion systems monitor the fluid level in the perfusion circuit reservoir using a level sensor in order to infer that air emboli are present when the level in the reservoir is too low. It is known to display or sound an alert signal when the level in the reservoir drops below a predetermined threshold limit (or when emboli are otherwise detected, such as with an ultrasonic sensor). In response to the alarm, the circulation is manually stopped by a health care professional (such as a perfusionist) as quickly as manually possible. Special steps must then be taken to remove the air emboli before restoring the circulation back to the patient.
The perfusionist has many tasks to perform in the operating room during cardiac surgery and the corresponding distractions can lengthen the response time for stopping circulation when an alarm is triggered. Therefore, there is a need in the art for a means of automatically stopping the emboli before it reaches the patient without having to wait for action from the perfusionist.
Besides the need to quickly divert any emboli from reaching the patient, it is very important to clear the emboli from the blood in the perfusion circuit so that circulation to the patient can be restored as soon as possible. Once circulation is stopped in the perfusion circuit, it is time consuming for the perfusionist to isolate the quantity of blood containing the emboli and remove the emboli. Therefore, there is also a need in the art for a means of quickly purging emboli in order to safely restore blood circulation to the patient.